The field of the invention is contact modules, and particularly, convertible contact modules for electromagnetically operated line contactors and relays.
In electromagnetic relays such as that disclosed in U.S. Pat. No. 3,251,964 issued to L. E. Lawrence et al in 1966, one or more sets of stationary and movable contacts, or poles, are mounted to a common frame and operated by an armature which is driven by an electromagnet. Each pole is an integral unit, or module, and as disclosed in U.S. Pat. No. 3,238,341 issued to J. L. Haydu in 1966, such contact modules may be mounted to the relay frame in either of two orientations. In one orientation, the contacts are normally opened, and by inverting the module the contacts are converted to normally closed. Other relays having convertible contact modules are disclosed in U.S. Pat. Nos. 3,453,571 and 3,519,967.
Convertible contact modules include terminal screws which are used to fasten wires to contact terminals that extend from each end of the module. In many cases, the same terminal screws hold the module in place. With prior modules these terminal screws must be completely removed from the module and reattached in a different opening or through the same opening, but in the opposite direction when the module is inverted so that the terminal screws will be easily accessible. When wiring a relay panel containing tens or hundreds of such terminal screws, this converting procedure can become time consuming, particularly when terminal screws are occasionally dropped and lost.